lower fuel mileage since fixed

I recently had my 2001 Pontiac Montana at the dealer where they replaced the engine manifold head gasket and put a new condensor in the air conditioner. Before they worked on it we averaged 22-24 mpg. Now we get around 17-18 mpg. We have not been using the air conditioner, just the vent. I took it back and they said they couldn't find anything wrong with it. Does anyone have any idea why we're getting around a 100 miles less per tank?

I'm curious, because I just had the condensor replaced in mine as well. Did they say what caused your condensor to leak? I'm wondering if this is common. I'll let you know how I find my mileage - although, to be fair, I have been using the a/c - but I haven't seen a huge drop in my mileage at this point.

Ted

I'm not a service tech, but it could be that your AC compressor is not cycling properly. During normal operation, your AC compressor clutch should only engage and draw power when your system is "requesting" air compression for the cooling system. If your compressor is running constantly, regardless if you only have the vent on, your mileage will drop. Perhaps they hooked up the new compressor improperly?

hth, Tom

For one thing the compressor wasn't changed. Another the compressor isn't touched when changing the condensor. Yes the condesnor leaking is a common problem. I do at least 3 condensors a week on the A and B platform mini vans.

If the compressor is cycling constantly than that would show a low charge condition.

How do you know if it has a low charge condition?

if AC compressor is low..you will hear a clicking sound frequently, its trying to build up pressure inside.

I am having the same poor gas mileage problem with my 2000 montana..new intake gasket was installed. New thermostat installed. oil changed.
I also noticed the mechanic did not close the bracket for the air filter proper.

Please check the last post date of the thread and avoid posting in that thread if the last post date is beyond 3 months from the current date. This thread is nearly 4 years old.You can start a new thread and link to the old one if you have new info .
Closed.